Error during model running

Hi Cris, I'm developing a model in integrated reservoirs. My study area has a characteristic that two reservoir is linked each other by connected water way. In the model, I'm going to consider bathymetry as two waterbody in the model. I already developed the model which is comprised of one waterbody. However, when I seperated the waterbody from one to two, the fatal error was triggered unlike one waterbody model that is no error(i.e. insufficient segments in branch, negative surface layer thickness). All introduced parameters are same in the two models(one waterbody, two waterbody). I'm very curious the reason. Could you explain why this result take place? Is there any missing point in developing the model? Sincerely Kyung.